Phthalocyanine compounds are useful as coatings, printing inks, catalysts or electronic materials. In recent years, they have been extensively studied particularly for their use as electrophotographic photoreceptor materials, optical recording materials and photoelectric conversion materials.
In the field of electrophotographic photoreceptors, there has recently been an increasing demand to extend the photosensitive wavelength region of conventional organic photoconductive materials to a longer side of near infrared light (780 to 830 nm) which corresponds to a wavelength region of a semi-conductor laser so as to make them applicable to a digital recording system, such as a laser printer. From this point of view, there have been reported photoconductive materials for semi-conductor lasers, such as squarylium compounds as disclosed in JP-A-49-105536 and JP-A-58-21410, triphenylamine type tris-azo compounds as disclosed in JP-A-61-151059, and phthalocyanine compounds as disclosed in JP-A-48-34189 and JP-A-57-148745 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
In cases where an organic photoconductive material is used as a photosensitive material for semi-conductor lasers, they are required to have a photosensitive wavelength region extended to a longer side and to provide a photoreceptor having satisfactory sensitivity and durability. None of the above-described conventional organic photoconductive materials sufficiently satisfies these requirements.
In order to overcome the drawbacks of the conventional organic photoconductive materials, the relationship between their crystal form and electrophotographic characteristics has been studied. In particular, many reports have been made on phthalocyanine compounds.
It is known that phthalocyanine compounds generally exhibit several different crystal forms depending on the process of production or the process of treatment and that the difference in crystal form has a great influence on their photoelectric conversion characteristics. For example, known crystal forms of copper phthalocyanine compounds include .alpha.-, .pi.-, .chi.-, .rho.-, .gamma.-, and .delta.-forms as well as a stable .beta.-form. These crystal forms are known capable of interconversion by a mechanical strain, a sulfuric acid treatment, an organic solvent treatment, a heat treatment, and the like as described, e.g., in U.S. Pat. Nos. 2,770,629, 3,160,635, 3,708,292, and 3,357,989. Further, JP-A-50-38543 refers to the relation between a crystal form of copper phthalocyanine and electrophotographic characteristics.
JP-A-62-119547 discloses an electrophotographic photo-receptor using a dihalogenotin phthalocyanine compound as a charge generating material. JP-A-1-14405 discloses a tin phthalocyanine compound having specific peaks on its X-ray diffraction pattern and an electrophotographic photoreceptor using the same. JP-A-62-119547 discloses a tin phthalocyanine compound having X-ray diffraction peaks at Bragg angles of 8.4.degree., 12.2.degree., 13.8.degree., 26.5.degree. and 28.2.degree., wherein the peaks at 26.5.degree. and 28.2.degree. have substantially equal intensity.
However, any of the known phthalocyanine compounds proposed to date is still unsatisfactory in photosensitivity and durability when used as a photosensitive material.